The occurrence of oil spills has steadily increased with the increased use and transport of oil. Over the past twenty years, a great deal of work has been carried out on devices and methods to deal with oil spills and clean-ups. Many different mechanical devices for collecting oil from the surface of the water, called generally skimming devices, have been devised, such as adhesive surface devices, porous surface devices, continuous belt devices, centrifugal devices and many more. No one device is useful for the mechanical recovery of every type of oil spill, however. The principal factors which determine the nature of the skimming device required are the size and the location of the spill. Large spills in open sea require different equipment than spills on sheltered waters. No single set of equipment is recommended in the presently available literature as the best for both sheltered water spills and spills at sea.
U.S. Pat. No. 3,618,768, issued to Brown on Nov. 9, 1971 teaches the use of a floating helical or screw-type conveyor attached at one end to a first vessel by a universal pivot, such as a ball joint, and at its other end to a second vessel having a motor for rotating the conveyor, and a collection tank for containing fluids and debris which are collected by the conveyor. The conveyor is used as a helical pump to pump fluid and debris collected by the conveyor by encasing the conveyor in a tube at one end. The collected fluids and debris are thus delivered into the reservoir on the second boat. In another embodiment, the conveyor is enclosed in a flexible tubing having a longitudinal opening on one side for admitting the oil from the surface of the water. The helical conveyor in Brown, however, is not used itself to separate oil from water, but merely to transport whatever material comes into contact with it. Separation is accomplished by slots in the casing of the conveyor, or by skilful movement and location of the equipment.
Various other devices are taught in the prior art which incorporate rotating spiral screws for the removal of impurities from water. French patent no. 1,314,495 issued to Bechard on Nov. 29, 1961 teaches a spiral screw having its lower ends supported by a central float for transporting floating materials such as oil, fats, and foams to a receiver where they are extracted. As in the Brown apparatus, the spiral screw is merely used as a conveyor and not as a separator mechanism. Similarly, U.S. Pat. No. 4,151,081 issued to Bolli et al. on Apr. 24, 1979 teaches the use of a spiral screw in conjunction with a partitioned housing to skim oil from the surface of water. U.S. Pat. No. 4,196,087 issued to Gordon on Apr. 1, 1980 teaches the use of spiral screw assemblies for conveying floating liquids to a central filtering mechanism. Again, the screws act merely as conveyors and do not themselves act to separate oil from water.